XPTI Vulnerability in Xen Hypervisor Affecting Guest Page Table Isolation
CVE-2026-79609

8.8HIGH

Key Information:

Vendor

Xen Project
Status
Xen Project
Vendor
CVE Published:
13 October 2026

What is CVE-2026-79609?

The vulnerability involves a flaw in the Xen Hypervisor's implementation of Xen Page Table Isolation (XPTI), which was designed to mitigate Meltdown vulnerabilities. The issue arises from the handling of 64-bit paravirtualized (PV) guest page table entries copied from guest-specified root page tables to those chosen by Xen. Given that the PV guest’s directmap does not encompass all memory due to segmentation beyond the 5 TiB address boundary, this creates potential lapses in protection, enabling unauthorized access to memory regions that should be isolated.

Affected Version(s)

Xen consult Xen advisory XSA-516

References

https://xenbits.xenproject.org/xsa/advisory-516.html

CVSS V3.1

Score:
8.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

This issue was discovered by George Dunlap.
.